Airplane propellers often use a hub for mounting a plurality of propeller blades on a drive shaft driven by an engine. Some propeller hubs have provision for pitch control to allow adjustment of blade pitch as the propeller rotates. Airplane propellers spinning at high rates with pitch adjustment subject hub components to a variety of relatively significant loads, including centrifugal force produced by the blades. To react these loads, prior hubs utilized relatively heavy components and closely coupled, roller bearings that use wet lubricants and a separate aerodynamic fairing to direct the airflow around the hub.
A variety of new airplane designs require reductions in the size and weight of components, including propeller hubs. For example ultra-light weight, high altitude, long range airplanes may require lighter weight components, including propeller hubs, in order to meet performance specifications. Existing designs for propeller hubs employ components that may be too large and/or too heavy for use in these applications. In addition, the exceptionally cold temperatures encountered at high altitudes increase the viscosity of wet bearing lubrication, which in turn reduces the efficiency of the propeller.
Accordingly, there is a need for a compact propeller hub that employs light-weight components, and which reduces or eliminates the need for wet lubricated bearings.